This invention relates to anti terrorist barricades capable of stopping the movement of vehicles unauthorized to enter a trafficway. A vehicle moving toward such a barricade has a certain kinetic energy which is a measure of the hitting power it posseses. This kinetic energy is calaculated from the vehicle weight and velocity, and on impact with such a barrier the kinetic energy is then converted into heat, sound and deformation of the vehicle, and in some cases deformation of the barrier. In actual practice, the total energy dissipation depends upon varying factors prevailing at the moment of impact, all of which need not be detailed here. However for example, a vehicle moving at 50 mph has twenty five times as much kinetic energy as it would have moving at 10 mph; or for example an armored car weighing thirty times as much as a small passenger car and moving at 10 mph would have less kinetic energy than said passenger car moving at 60 mph. It is within this approximate range of kinetic energy with which this invention is primarily concerned, it being a general object to provide a retractile bollard that is configured to provide maximum protection against vehicle assault within a minimum package or installation area.
In accordance with this invention, the bollard is a structural steel fabrication that is lifted into working position by a directly coupled double acting cylinder and piston means, so that it can be positively extended and retracted. The geometry of the bollard is disposed and rotatably oriented so that the energy of impact is efficiently transmitted into a rugged foundation that absorbs said energy, within its elastic limit that exceeds the rupture point of the bollard under the same impact conditions. Accordingly, under major impact conditions the bollard per se may be damaged or destroyed and it is therefore considered to be expendable and adapted to be readily replaced. It is an object of this invention, therefore, to provide a barrier of unit construction wherein the components thereof are individually replaceable.
The retractile bollard of the present invention is characterized by the aforesaid foundation and by a mounting frame by which the bollard is installed in said foundation. A feature is the flush trafficway condition of this barrier unit, when the bollard is retracted, and to this end the assembled condition of components as they are dislosed herein provides the accessability for disassembly and repair, service and replacement. It is an object of this invention to provide for this accessability and replaceability.
The bollard is power operated by lift means, preferably a hydraulic power and electrical control system later described. However, the term "lift means" is to include such means as screw jack, chain and sprocket, cable and drum, and rack and pinion, or the like lift means. In practice, operation is from bottled gas, by air from a compressor and/or reservoir of compressed air, or by a hydraulic pump or liquid accumulator, as will be described. A feature of this barrier system is its capability of instantaneous operation when circumstances require.
The typical collision point above grade is presumed to be approximately 17 inches, the average height of a vehicle bumper. Accordingly, the bollard is extended well above the point of collision, for example to a height of about two feet, all of which may vary as required. The actuation of the bollard between the vertically extended and the retracted position is by fluid actuator, it being an object to minimize motor power as well as pump rate requirements. With the preferred form of bollard motivation, a fluid pressure accumulator is employed, and wherein liquid is stored between predetermined high and low pressure levels, as potential energy available for instantaneous action. As disclosed herein, there is a high-low pressure sensor that automatically controls operation of the motor pump means that maintains a predetermined range of pressure in an accumulator. The lift motor for the bollard is a positive displacement hydraulic cylinder and piston means, activated through electrically energized valves for instantaneous response. The hydraulic lift system used herein is the subject of my copending application Ser. No. 488,106 filed Apr. 25, 1983, entitled HYDRAULIC SAFETY BARRIER TRAFFICWAY CONTROLLER, issued Dec. 25, 1984 as U.S. Pat. No. 4,490,068.
A feature of this barrier unit installation is that it is self bailing and rids itself of the accumulation of surface waters. By cycling the barricade bollard, most of the surface water entering into the foundation pit can be forced out. If there is no gravity drain or pump out, the water level after cycling will be minimized. This is below any of the moving elements but may be above the clevis of the cylinder. Although some oxidation may occur at the clevis, only long term exposure will adversely affect operation. A permanent drainage means is preferable as shown, so that all waters are disposed of.